The present invention relates to a method for the manufacture of an electronic component and a circuit-board construction.
The invention particularly relates to a manufacturing method, in which one or more components are embedded in an installation base. The electronic module being manufactured can be a module like a circuit board, which contains several components, which are connected to each other electrically through conductor structures manufactured in the electronic module. In particular, the invention relates to an electronic module, which contains microcircuits, to which several contact terminals are connected. Of course, in addition to, or instead of microcircuits, other components too, for example passive components, can be embedded in an installation base. The intention is thus to embed in the electronic module components that are typically attached uncased to a circuit board (to the surface of the circuit board). Another important component group consists of components that are typically encased for attachment to a circuit board. The electronic modules, to which the invention relates, can of course also include other kinds of components.
The installation base can be of a type that is generally used in the electronics industry as a base for installing electrical components. The tasks of the base are to provide a mechanical attachment base for the components as well as the necessary electrical connections, both to the other components on the base and to those outside the base. The installation base can be a circuit board, so that the structure and method to which the invention relates are closely associated with circuit-board manufacturing technology. The installation base can also be some other base, for example, a base used for packaging a component or components, or the base of a complete operational module.
Circuit-board manufacturing technology differs from the manufacture of microcircuits, for instance, in that, in the manufacturing techniques of microcircuits, the installation base, that is a substrate, is a semiconductor material, whereas the basic material of the installation base of circuit boards is some kind of insulation material. The techniques for manufacturing microcircuits are also typically considerably more expensive that those for manufacturing circuit boards.
The casings and packages of components and particularly semiconductor components differ from the construction and manufacture of circuit boards, in that the primary purpose of component packages is to form a casing around the component, which will protect the component mechanically and facilitate the handling of the component. On the surface of the component casing, there are connection parts, typically protrusions, with the aid of which the cased component can be easily correctly aligned on the circuit board and the desired connections created to it. In addition, there are conductors inside the component case, which connect the connection parts protruding outside the case to the connection areas on the surface of the actual component, through which the component can be connected as desired to its surroundings.
However, the cases of components manufactured using this traditional technology demand a considerable amount of space. As the size of electronic devices has diminished, attempts have been made to get rid of component cases, which not only demand much space, but are also unnecessary and lead to needless costs. To solve this problem, various constructions and methods have been developed, with the aid of which components can be located inside the circuit-board structure.
Known methods, in which components are embedded in an installation base during the creation of the base, are disclosed in patent application publication WO 03/065778 and WO 03/065779, as well as in patent publications U.S. Pat. Nos. 6,038,133 and 6,489,685. The methods disclosed in these publications can be used to manufacture, for example, multi-layer circuit boards, inside which integrated microcircuits, for example microprocessors and memory circuits, are embedded.
In the known methods, a problem can arise with the heating of the microcircuits inside the installation base. During operation, microcircuits and particularly certain microprocessors produce a significant thermal output, which must be conducted away from the circuit to prevent the circuit from overheating. This is because overheating in a circuit can endanger its reliable operation. When circuits are installed, according to the traditional technique, on the surface of a circuit board, it has been possible to conduct the thermal output to the surrounding air, or attach a suitable heat sink to the circuit. If a circuit is embedded inside a circuit board, the basic material of the circuit-board, which has relatively poor thermal conductivity, will surround the circuit. The thermal output cannot then be easily conducted to the surrounding air, nor is it easy to attach a heat sink to the circuit. The thermal output produced by the circuit will spread from the microcircuit to the surrounding circuit-board material through direct contact and through the buses connected to the circuit.